The meals ready to eat in the military can be heated on a flameless heater. You can purchase a similar product called heater meals. Just pour water into the heater unit wait a few minutes and you have a hot meal. The source of energy is Mg(s) + 2H2O(l) > Mg(OH)2(s) + H2(g)
Calculate the enthalpy change under standard conditions, in joules, for this reaction. What quantity of magnesium is needed to supply the energy required to warm 25ml (1.00g/ml) from 25C to 85C?
Now the first part I calculated -352.88kj for the enthalpy change, which was correct. Now when I get to the second part I have some trouble. Normally I would set it up as
q1+q2=0 Where the energy release and absorbed equal zero because both come to thermal equilibrium. So I proceed with naming q1 the water.
q1= (4.184J/g. C)(25g)(60C)= 6276J. So in order to increase 25g of water 60C, you need 6276J. Now this is where I am stuck, the problem doesn't give the specific heat capacity for the magnesium, so I looked it up and did this
q2= (1.20J/g. C)(x)(60)... now this is where I think i did something wrong, not only because when i do this i do not get the right answer, but because the temperature values for the magnesium were not given. Can someone help me out with this problem? I feel I have to use the enthalpy change value to eventually get the amount of Magnesium required.